How do i become tall fast?

Guys im actually short 4 ma age.Im 18 yrs old but im not tall enuf.Ive heard ppl sayin tht guys hav growin age uptil 21yrs,is it true?If its true thn suggest me the bst way 2 grw fast,the most effective one.Ppl normally tel me 2 do cycling,pull ups,jumps-(bringing knees as high as the chest while jumpin),drinking milk.etc. Ok so out of these,whch is the fastest,most effective way 2 grow?Pls reply.I dnt wanna grow too tall,but atleast i wanna increase by an inch or three.Pls any ideas?